Masamitsu Kataoka

Potentiometric Liquid Membrane Sensors That Discriminate Linear Homologs and Geometrical/Positional Isomers of Dicarboxylates

Abstract Potentiometric discrimination of series of linear homologs (4-7), geometrical isomers (8,9), and positional isomers (10-12) of dicarboxylate guests by a liquid membrane sensor containing Iipophiiic macrocyclic polyamine 1 as a sensory element is described. the pH conditions were carefully set so that the potentiometric response to the dianionic forms of the guests could be specifically observed. Whereas only small discrimination was observed for the flexible linear homologs (4-7), marked discrimination was observed, for the geometrical isomers (8,9) and positional isomers (10-12) having rigid structures. the selectivities of the potentiometric response were found to correlate well with the reported selectivities of host-guest complexation in water displayed by macrocyclic polyamines having the structures related to 1.

Biomimetic ion-channel sensors based on host-guest molecular recognition in Langmuir-Blodgett membrane assemblies

Abstract Biomimetic “ion-channel sensors” based on host-guest molecular recognition were constructed by incorporating several kinds of receptor molecules in Langmuir-Blodgett (LB) molecular assemblies deposited directly on glassy carbon electrodes. The receptors used were valinomycin, bis(crown ether)s, macrocyclic polyamine and cyclodextrin polyamine. The binding of charged stimulants (metal ions, inorganic and organic anions) to these receptors induced a marked increase (or decrease) in the ion permeability of the membranes, as detected by cyclic voltammetry using [Fe(CN) 6 ] 4- or [Ru(bpy) 3 ] 2+ as marker ion. Such a mode of response, corresponding to model “channel opening (or closing)”, can be explained on the basis of the charge-charge interaction involving the stimulant, marker ion and lipid.

Chemical sensing based on membrane potential change induced by host-guest complexation at a membrane surface1

Abstract Three new principles for discrimination of organic guests by the membrane potential change are described, which are based on the host-guest recognition of charged groups, hydrogen bonding groups, or steric shapes of nonpolar moieties. (i) Potentiometric discrimination by the recognition of charged groups has been attained by liquid membrane type electrodes containing lipophilic macrocyclic polyamines as the sensory elements. These electrodes displayed potentiometric selectivities for organic anions according to the amount or proximity of negative charges. Thus, the strongest responses were observed for such guests as ATP4- having a large number of negative charges as well as maleate2- and phthalate2- having negative charges at the closest distance within the molecule. (ii) Potentiometric discrimination by the recognition of hydrogen bonding groups has been attained by an electrode containing a lipophilic cytosine-pendant triamine, which functions as a ditopic receptor for guanine nucleotides by a...

Catalytic determination of molybdenum(VI) by means of an iodide ion-selective electrode and a landolt-type hydrogen peroxide-iodide reaction.

A trace amount of molybdenum(VI) can be determined by using its catalytic effect on the oxidation of iodide to iodine by hydrogen peroxide in acidic medium. Addition of ascorbic acid added to the reaction mixture produces the Landolt effect, i.e., the iodine produced by the indicator reaction is reduced immediately by the ascorbic add. Hence the concentration of iodide begins to decrease once all the ascorbic acid has been consumed. The induction period is measured by monitoring the concentration of iodide ion with an iodide ion-selective electrode. The reciprocal of the induction period varies linearly with the concentration of molybdenum(VI). The most suitable pH and concentrations of hydrogen peroxide and potassium iodide are found to be 1.5, 5 and 10mM, respectively. An appropriate amount of ascorbic acid is added to the reaction mixture according to the concentration of molybdenum(VI) in the sample solution. A calibration graph with good proportionality is obtained for the molybdenum(VI) concentration range from 0.1 to 160 muM. Iron(III), vanadium(IV), zirconium(IV), tungsten(VI), copper(II) and chromium(VI) interfere, but iron(III) and copper(II) can be masked with EDTA.

Liquid-membrane dodecylbenzenesulphonate ion-selective electrode employing Victoria Blue as the counter-ion

The dodecylbenzenesulphonate anion forms an ion-pair with the Victoria Blue cation and this is easily extracted into nitrobenzene. It was found that the calibration curve of the dodecylbenzenesulphonate ion-selective electrode based on this system shows good linearity in the range 10(-3)-10(-7)M. Selectivity coefficients were evaluated for some anions. The results indicated a poor tolerance towards dodecyl sulphate, perchlorate and periodate. Dodecyl sulphate, dodecylbenzenesulphonate and several kinds of synthetic anionic detergents have been successfully titrated potentiometrically with a solution of Zephiramine (benzyldimethyltetradecylammonium chloride) by using the electrode as an indicator electrode.

Construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of α-diols and α-amino-alcohols

Abstract The construction of a liquid-membrane type periodate ion-selective electrode and its application to the potentiometric titration of α-diols and α-amino-alcohols are described. The ion-pair of periodate anion with Capriquat (tri-n-octylmethylammonium chloride), is easily extracted into nitrobenzene, and this extract is employed as a liquid ion-exchange membrane. The calibration curve shows Nernstian response towards periodate ion over the concentration range from 10−1 M to 10−7 M with a slope of 60 mV/pIO−4. Selectivity coefficients with respect to various ions were evaluated. The electrode potential was independent of pH in the range 2.5–7.5. Some α-diols and monoethanolamine were successfully titrated potentiometrically with the aid of the present electrode.

Construction of a permanganate ion-selective electrode and its application to potentiometric titrations

The construction of a liquid-membrane type permanganate ion-selective electrode and its application to potentiometric titrations are described. The benzylcetyldimethylammonium-permanganate ion-pair in the aqueous phase is easily extracted into nitrobenzene and the extract is employed as the liquid ion-exchange membrane of the ion-selective electrode. The electrode gives Nernstian response to permanganate in the concentration range from 10(-6) to 10(-1)M, and the potential is almost independent of pH over the range from 3.0 to 10.5. The electrode can be used as indicator electrode in potentiometric titrations with permanganate.

Chromazurol S ion-selective electrode for chelatometric titration

A liquid membrane type Chromazurol S ion-selective electrode has been constructed and applied to chelatometric titrations. In aqueous medium, zephiramine (benzyldimethyltetradecylammonium chloride) forms with the anion of Chromazurol S an ion-pair which is easily extracted into nitrobenzene. The extract is used as the liquid ion-exchanger for the Chromazurol S ion-selective electrode. The most suitable ion-pair concentration in the liquid ion-exchanger membrane is 10(-4)M. The linear Nernstian-response range of the Chromazurol S anion in aqueous solution is 10(-2)-10(-6)M. The electrode has been successfully applied to the chelatometric titration of Cu(II), Ni(II), Fe(III) and Pb(II) with EDTA.

CHEMICAL SENSOR MECHANISMS: EXPERIMENTAL APPROACHES

ABSTRACT Some new principles for the development of novel “biomimetic sensors” are discussed that are based on the mechanisms of molecular recognition and information transduction/amplification at biological cell membranes, displayed by receptors, active transport carriers, and ion-channels. Thus, the development of a potentiometric sensor for organic anions and neutral molecules using macrocyclic polyamine as a sensory element, the generation of membrane potential at lipid bilayers by neutral hydrophobic odorants, and some new strategies for sensors with built-in signal transduction/amplification functions (uphill transport membrane sensors and ion-channel sensors) are described.